1. Field of the Invention
This invention relates to a charging member used in contact charging of electrophotographic apparatus, and a process for producing the same, and to a process cartridge and an electrophotographic apparatus.
2. Description of the Related Art
At present, a contact charging method has been put into practical use as one of methods for charging the surface of an electrophotographic photosensitive member electro-statically. The contact charging method is a method in which a voltage is applied to a charging member disposed in contact with the electrophotographic photosensitive member, to cause micro-discharge at the part of contact between the charging member and the electrophotographic photosensitive member and the vicinity thereof to charge the surface of the electrophotographic photosensitive member electrostati-cally.
In the contact charging method, in order to improve charging efficiency and uniform charging performance to the electrophotographic photosensitive member, it is necessary to sufficiently and uniformly secure a contact nip between the electrophotographic photosensitive member and the charging member. For such requirement, a charging member has conventionally been proposed which has a substrate and a conductive elastic layer provided on the substrate. Such a conductive elastic layer, however, often contains low-molecular weight components in a relatively large quantity, and hence such low-molecular weight components may bleed out to contaminate the electrophotographic photosensitive member and charging member. Accordingly, in order to keep the low-molecular weight components from bleeding out, a surface layer is provided on the conductive elastic layer in some cases.
A toner, an external additive, discharge products and paper dust which have deposited on a cleaning member for the electrophotographic photosensitive member may also slip through there to contaminate the charging member standing in contact with the electrophotographic photosensitive member. As the result, non-uniform charging comes about to cause lengthwise streaky images.
Japanese Patent Application Laid-open No. 2002-080785 discloses that a conductive filler is made to disperse in an organic-inorganic hybrid film formed by a sol-gel process and this makes the film have a larger contact angle to water to improve its release properties to the toner.